Slitting mechanism for use with circular knitting machines

ABSTRACT

A mechanical slitting mechanism is provided with first and second cutting elements arranged beneath a dial assembly of a circular knitting machine so as to provide for controlled cutting of a tubular fabric being knitted by the machine. Rack and pinion mechanisms are utilized for imparting controlled reciprocations to the first cutting element relative to the second cutting element. A free end portion of the reciprocating cutting element is shielded from the tubular fabric so as to prevent snagging of the fabric during cutting operations.

[ Oct. 30, 1973 I SLITTING MECHANISM FOR USE WITH CIRCULAR KNITTING MACHINES [75] Inventor:

[73] Assignee: Burlington Industries, Inc.,

Greensboro, N.C.

22 Filed: Feb. 28, 1972 21 App]. No.: 229,897

Vaughn H. Butler, Harriman, Tenn.

2,810,280 10/1957 Rossman 66/147 3,522,715 8/1970 Merritt et a1. 66/147 X 3,714,800 2/1973 ,Mazzi 66/147 Primary Exaiminer-Robert R. Mackey Attorney-John W. Malley et al.

[57] ABSTRACT A mechanical slitting mechanism is provided with first and second cutting elements arranged beneath a dial 52 us. Cl. 66/147, 26/55 wc, 83/629 assemblyof a circular knitting machine as P 51 Int. Cl .I D04b 35/34 vide controlled cutting Of a tubular fabric being 58 Field of Search 66/147; 26/55 wc; knitted by machine- Rack and P mechanisms 83/629 are utilized for imparting controlled reciprocations to the first cutting element relative to the second cutting 55 References Cited element. A free end portion of the reciprocating cut- UNITED STATES PATENTS ting element is shielded from the tubular fabric so as to prevent snagging of the fabric during cutting operal,064,929 6/1913 Pond 83/629 X tions 1,714,382 /1929 Lebovitz.... 83/629 X 2,095,172 10/1937 Dale 83/629 X 11 Claims, 7 Drawing Figures '3 F .53 H lllll \m z 5 'I 5 I I I T l l l l I I A? J 3 I :1 V L Ei:r 25

I 4 -I l 0 l 1 gp W PAIENIEUncI 30 ms SHEET 2 OF 3 a4 .4 W: a

a 5.! w m Mi mama SLITTING MECHANISM FOR USE WITH CIRCULAR KNITTING MACHINES BACKGROUND AND BRIEF DESCRIPTION OF INVENTION This invention is directed to improvements in slitting mechanisms for use with circular knitting machines.

As is known in this art, slitting mechanisms are utilized in combination with circular knitting machines to provide a cut or slit along a longitudinal line of a tubular fabric being knitted by the machine. The longitudinal cut may be a continuous cut to convert the tubular product of the machine into a non-tubular flat form, or the cut may be provided at selected intervals so that final products of special form can be created from the tubular product of the machine. For example, in the manufacture of one-piece panty hose garmentsit is desirable to provide for a cutting of a tubular fabric for a certain length of knitting of the fabric, followed by no cutting of the fabric for an additional length of knitting, to thereby produce a structure which can be finished as a panty hose garment.

The slitting mechanism of the present invention is of a type which imparts a mechanical cutting action to a pairof cutting elements so as to effect the cutting of a slit along the length of a tubular knitted fabric as the fabric is produced by a known circular knitting machine. Mechanical slitting devices have been proposed for use in circular knitting machines, as evidenced, for example, by Italian Pat. 841,972. However, known devices in this art have been somewhat complex in their requirements for numerous linkages for controlling and operating cutting elements which must coact to effect a cut of a knitted fabric, and this has resulted in a certain amount of unreliability and difficulty in maintenance of devices of this type.

The present invention departs from prior suggestions for slitting mechanisms by its use of relatively simple driving and control arrangements for the cutting element portions of the mechanism. The slitting mechanism of this invention is easily manufactured with a minimum number of components to be assembled and maintained, and the operation of the mechanism is completely satisfactory from a standpoint of reliability of operation.

In accordance with the present invention, a cutting means is supported beneath the dial assembly of a standard circular knitting machine so as to provide for a controlled cutting of a tubular fabric as the fabric descends past the position of the cutting means. The cutting means includes a pair of cutting elements which coact upon reciprocation of one of the elements to effect a cutting of a portion of the fabric which is engaged between the two cutting elements. The reciprocating cutting element is generally hook-shaped, and includes an inwardly directed cutting edge which coacts with an outwardly directed cutting edge of the second cutting elements The reciprocating cutting element is positively positioned and reciprocated by a pinion gear which receives driving motions from a vertically disposed rack and which transmits such driving motions to the reciprocating cutting element by means of a second rack associated with the cutting element itself. The driving arrangement is easily controlled to impart precise reciprocations to the cutting element. The entire slitting mechanism assembly, and its associated actuating devices, can be fitted to existing circular knitting machines without interference with normal operation and maintenance of such machines.

In a preferred form of the invention, the slitting mechanism includes first and second cutting elements which coact to effect a cut in a knitted fabric at a point where the knitted fabric is engaged by the cutting elements beneath the dial assembly of a circular knitting machine. The first cutting element is mounted to reciprocate relative to the second cutting element along a line generally perpendicular to a line of travel of the knitted fabric as the knitted fabric descends downwardly past the level of the cutting elements. Support means are provided for suspending the cutting elements beneath the dial assembly, and actuating means are included for controlling cutting functions of the cutting means. A shielding means, in the form of an annular collar having a slot formed therein, is mounted within the cylinder portion of the circular knitting machine to provide for a shielding of a free end portion of the first cutting element within the slot formation so as to prevent a snagging of the tubular fabric as the fabric is being cut.

In a typical operation of the mechanism of the present invention, one cutting element is extended into a cutting position before knitting of the tubular fabric commences. Then the extended cutting element is reciprocated in cooperation with the second cutting element to effect a slitting of the tubular fabric as the fabric reaches the level of reciprocation of the cutting element. When a desired length 'of slit has been formed the extended cutting element is retracted so as to be fully withdrawn out of the line of travel of the tubular knitted fabric. In another type of operation the reciprocating cutting element can be designed to penetrate the tubular fabric while it is being knit so that slits can be formed at an intermediate point along the length of a knitted tubular fabric.

Additional features and advantages of the present invention will be discussed in greater detail hereinafter, and in that discussion reference will be made to the acompanying drawings as briefly described below.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a side elevational view, partly in cross section, showing positioning of the slitting mechanism of this invention relative to a dial and cylinder assembly and associated drive train of a circular knitting machine;

FIG. 2 is a front elevational view of a portion of the assemblies shown in FIG. 1, in enlarged scale from what is shown in FIG. 1;

FIG. 3 is a top plan view of the slitting mechanism assembly of this invention, as seen on line 3-3 of FIG. 1, but shown in enlarged scale from what is shown in FIG. 1;

FIG. 4 is a sectional view in elevation of the assembly shown in FIG. 3, as seen on line 4-4 of FIG. 3, showing a cutting element of the mechanism in an extended position;

FIG. 5 is a view similar to FIG. 4 with the cutting element ofthe slitting mechanism retracted to an intermediate position from the position shown in FIG. 4;

FIG. 6 is a greatly enlarged sectional view of a portion of the slitting mechanism assembly, as seen on line 6-6 of FIG. 4; and

- FIG. 7 is a greatly enlarged sectional view of a portion of the slitting mechanism, as seen in section on line 7-7 of FIG. 5.

DETAILED DESCRIPTION OF INVENTION Referring to FIG. 1, a slitting mechanism assembly 10 of the type contemplated by this invention is secured with bolts or other fastening means to a bottom surface of a dial assembly 12 of a circular knitting machine. The dial assembly 12 typically carries horizontally disposed transfer jacks (not shown) which cooperate with vertically disposed knitting elements carried around a cylinder 14 so as to allow a tubular form of fabric 16 to be knitted by the circular knitting machine in a known manner. The circular knitting machine which is illustrated is of a known construction and includes known and conventional means for rotating the dial assembly l2 and the cylinder 14 during a knitting operation.

The slitting mechanism 10, as further illustrated in FIGS. 3 7, comprises a frusto-conical housing 18 which can be mounted coaxially on the bottom side of the dial assembly 12. The housing 18 functions to carry a cutting means having a first cutting element 20 and a second cutting element 22 which coa'ct to cut a slit in a knitted fabric along a line where the knitted fabric descends downwardly past the position of the cutting elements during the knitting of the tubular fabric. FIG. 1 illustrates the overall relationships which exist when the cutting means of the slitting mechanism is in a position to effect a cut in the tubular fabric 16 being formed by the dial and cylinder assemblies of the circular knitting machine.

The cutting elements 20 and 22 are mounted in a slot formation within the housing structure 18 so that the first cutting element 20 can be reciprocated by a controlled drive mechanism while the second cutting element 22 is maintained in a fixed position relative to the housing. The two cutting elements are positioned in side-by-side contact with each other, as shown in FIGS. 3, 6 and 7, and are mounted in vertical planes offset from the center axis of the housing 18. The first cutting element 20 is generally hook-shaped with a cutting edge 24 directed inwardly towards a central portion of the assembly. The second cutting element 22 is provided with a cutting edge 26 (see FIG. 7) directed outwardly from the assembly in a position which is slightly within, but almost flush with the outer profile of the housing 18. The two cutting edges 24 and 26 may be regarded as generally vertically oriented, and it can be seen that a reciprocation of the cutting edge 24 past the fixed position of cutting edge 26 results in a slicing or cutting of any yarn or fabric material engaged between the two cutting edges during such reciprocation. In typical usage of the cutting mechanism 10, the movable cutting element 20 is extended outwardly of the housing (to the position shown in FIGS. 1 and 4) before knitting operation commences so as to be in a position to receive a terminal end of the tubular fabric which is produced by the circular knitting machine after knitting commences. Then, the movable cutting element 20 is reciprocated back and forth for a limited range of movements corresponding generally to the limits shown in FIGS. 4 and 5 to effect repeated cutting of successive coarses of the tubular fabric for whatever length of cut is desired in the article to be produced. When slitting is to be stopped, the movable element 20 is fully retracted into the housing 18 so as to be moved v out of the line of travel of the knitted fabric which continues to descend past the position of the slitting mechanism.

In an alternative use of the cutting mechanism 10, a pointed nose portion 27 of the cutting element 20 can penetrate a knitted portion of a fabric as the cutting element 20 is extended outwardly to its cutting position so as to initiate slitting of the fabric at some intermediate point along its length.

During reciprocations of the first cutting element 20 for producing a slit in a knitted fabric, the free end portion of the cutting element 20 is shielded within a groove 28 formed downwardly from a top edge of an annular collar means 30. The collar means 30 is shown in FIG. I as being mounted at the upper end of an inner sleeve 31 secured to the cylinder assembly 14 so that the collar means 30 rotates with rotations of the cylinder and dial assemblies. Thus, the collar means 30, with its groove formation 28 for receiving the terminal end of the first cutting element 20, functions as a shielding means for the free end portion of the first cutting element during cutting motions of the cutting element. This prevents unwanted snagging of the knit fabric by the slitting mechanism as the fabric descends past the cutting means of the slitting mechanism. FIG. 7 shows the relationship between the terminal end portion of the first cutting element 20 and the groove 28 of the shielding collar 30 when the cutting element 20 is retracted to its inner limit position during cutting reciprocations. It can be seen that the tip end of the cutting element 20 is shielded from contacting and snagging fabric even when the cutting element has been withdrawn to this limit position.

The cutting element 20 is positively reciprocated and controlled by novel actuating means which provides for a pinion or gear means for positively driving and positioning the first cutting element 20 relative to the line of travel of a knitted fabric past the position of the slitting mechanism 10 beneath the dial assembly of the circular knitting machine. This results in a very precise and reliable control of the reciprocating movements of the first cutting element 20. Basically, the actuating means for the cutting element 20 includes first and second rack elements 32 and 34, respectively, which are carried within the housing structure 18 so as to engage a single pinion means 36 mounted for rotation within the housing structure. The first rack means 32 is mounted in a bore formed coaxially with the centerline of the dial assembly 12 so as to impart reciprocal driving motions to the pinion means 36. The second rack means 34 is mounted on a generally horizontal axis so as to receive driving motions from the pinion means 36. The second rack means 34 is positioned to reciprocate the first cutting element 20. In the illustrated embodiment, the second rack means 34 is formed as a part of the cutting element 20 by attaching the rack means to, or forming it on, abase portion of the cutting element 20. In this manner, the cutting element 20 can be reciprocated by vertical reciprocations applied to the first rack element 32.

The first rack element 32 is connected to a pin means 38 which extends upwardly through the dial assembly 12 and its associated drive structures for ultimate connection to a series of linkages which transmit vertical reciprocations to the pin means 38. The pin means means 38 and its associated rack means 32 are arranged so that upward movement of the pin means to an upper limit position causes the first cutting element to be fully retracted inwardly out of the line of travel of a fabric being knitted by the circular knitting machine. The range of movement available to the pin means 38 and its associated rack means 32 is such that the pin means can be reciprocated adjacent to its lowermost limit position to reciprocate the first cutting element 20 back and forth in the line of travel of the fabric during a cutting operation. The limits of reciprocations adjacent to the lowermost limit position of the pin means 38 are represented by the limit positions shown in FIGS. 4 and 5 for the cutting element 20.

Control linkages for reciprocating the pin means 38 are shown in FIGS. 1 and 2. The upper end of the pin means 38 is provided with a pair of spaced collars 40, or their equivalents, to define a circumferential groove which receives a follower collar 42 carried by a lever 44. The lever 44 is pivotally connected at 46 to a conventional bracket 48 which supports the dial assembly 12, a coaxial drive shaft 50 of the dial assembly, and a radial shaft 52 of a disengageable gear train which effects drive of the dial assembly 12. A control rod 54 is secured to the lever 44 for lifting the lever 44 to an extreme upper limit position in accordance with a programmed sequence. The control rod 54 is secured to any suitable programming cam (not shown) to thereby raise and lower the cutter-operating pin means 38 to an uppermost position which fully retracts the cutting element 20 out of the cutting zone and to a lowermost position which permits limited reciprocations of the cutting element 20 in the cutting zone.

When the control rod 54 is lowered, the lever 44 is moved up and down by a cam 56 carried by the radial shaft 52 of the dial assembly drive train. The cam 56 contacts a roller type follower 57 mounted on a bracket 59 secured to the lever 44 to thereby lift and lower the lever as the cam 56 rotates with the drive shaft 52. The

cam 56 and follower 57 are maintained in continuous contact by atensioned spring means 55 extending between the lever 44 and the bracket 48. Thus, the reciprocation of the lever 44, and ultimately the cutting element 20, istimed with the driving means which rotates the dial assembly about its vertical axis. This provides for repeated cutting reciprocations of the cutting element 20 as fabric is being knitted by the rotating assemblies.

Referring again to FIGS. 3 7, additional details of construction and assembly of the slitting mechanism can be understood with reference to a specific example of the invention. In this example, the housing structure 18 comprises a solid block of metal material into which a slot 60 is formed for receiving the two cutting elements 20 and 22. The slot 60 can be easily milled into the block and completely traverses the block so as to be open at each end thereof. A vertically disposed bore 62 is formed coaxially on the centerline of the block to receive the first rack means 32 secured at the end of the pin means 38. A second bore 64 is formed on ahorizontal axis to receive the pinion 36, and the second bore intersects the bottom of the slot 60. A small bore 66 isformed from an outside surface of the frustoconical housing block to communicate with a side wall of the slot 60 so that a spring means 68 can be inserted therein for pressing against cutting element 22 to maintain a relatively tight contact between the cutting elements 20 and 22. An adjustable screw element 70 closes the end of the bore 66 to secure the spring means 68 therein and to provide for adjustment of compression of the spring means 68.

in assembling the mechanism of the illustrated embodiment, bearing plates 72 are inserted and fixed in the bottom of the slot 60 to provide a bearing surface for the cutting elements. Then, the cutting element 22 is secured in place with a pin 69 in. the slot 60, followed by insertion of the reciprocal cutting element 20 next to it. The top of the slot 60 is closed off with a wedgeshaped piece 74 which is shaped and dimensioned to cover both cutting elements and to close off the upper portion of the slot 60. All elements are held in place by a plate member 76 (see FIG. 6) which is fastened to the top of the housing block with screw fasteners. The first rack means 32 can be merely inserted into its bore 62, and the pinion means 36 is inserted into its bore 64. The pinion means includes a bore along its center axis for receiving a support pin 78, and in the illustrated embodiment, the support pin 78 is carried by a cap member 80 which functions to close off the bore 64 and. to maintain the pinion means 36 in a preferred position. The cap member 80 comprises a flat disc having a groove formation 82 in its outer face so that it can receive a tool for being turned about its axis. The periphery of the cap member 80 is provided with screw thread formations which mate with corresponding formations provided. in the end of the bore 64. Thus, the pinion means can be easily inspected, lubricated or removed by merely unscrewing the cap member 80 and with drawing the cap member and its associated support pin 78 from the bore which carries the pinion means. The support pin 78 is sufficiently long to extend past the position of the pinion so that its terminal end can be received into a smaller diameter bore 83 formed into the block on the center axis of the larger bore 64. During assembly of the various components, the first and second rack means 32 and 34 are placed in preferred positions corresponding to desired limits of travel for the cutting element 20, and these positions are maintained upon insertion of the pinion means 36 into its bore 64 with a mating of the pinion teeth with the tooth formations of the two rack means.

Having described the structural features of an exemplary embodiment of the present invention, it can be seen that the slitting mechanism of this invention is relatively simple in design and yet very precise and reliable in its action. The components of the slitting mechanism can be easily manufactured from suitable selections of metal or other materials, and all components can be designed to withstand long usage and wear with very little maintenance. It can be appreciated from the above discussion that the principles of this invention can be included in other embodiments of slitting mechanisms to provide for the positive control and ease of construction and maintenance features of this invention. Equivalent variations in the structural features which have been discussed above are intended to be included within the scope of protection defined in the claims below.

What is claimed is:

l. A slitting mechanism for use with a circular knitting machine having a dial assembly rotatable in unison with a cylinder assembly for cutting a slit along the length of a tubular knitted fabric as the fabric is being knitted by the machine and descends through the cylinder assembly, comprising second rack means is formed as a part of said first cutting element so that driving motions of said pinion means are transmitted directly to said first cutting element.

support means includes a housing for enclosing said first and second rack means and said pinion means, said housing being secured to a bottom surface of the dial assembly of the machine so that said housing and its contained structures can rotate with rotational movements of the dial assembly about its centerline.

cutting means having first and second cutting elements which coact to effect a cut in a knitted fabric at a point where the knitted fabric is engaged by said cutting elements, said first cutting element being mounted to reciprocate relative to said sec- 0nd cutting element along a line generally perpendicular to a line of travel of the knitted fabric as the knitted fabric descends past the positions of said cutting elements,

support means for suspending said cutting means beneath the dial assembly of the circular knitting machine so that the cutting elements are mounted generally internally of the tubular knitted fabric being produced by the machine,

shielding means for shielding a free end portion of said first cutting element from contacting and snagging the tubular fabric being cut, and

actuating means operatively associated with the cutting means for controlling cutting functions of the cutting means.

2. The slitting mechanism of claim 1 wherein said actuating means includes a single pinion means mounted for rotation within said support means, first and second rack means carried within said support means and engaged with said pinion means, said first rack means being mounted on a generally vertical axis on the centerline of the dial assemblyso as to impart driving motions to said pinion means when said first rack means is reciprocated on its axis, and said second rack means being mounted on a generally horizontal axis so as to receive driving motions from said pinion means, and said second rack means being positioned to reciprocate said first cutting element.

3. The slitting mechanism of claim 2 wherein said 4. The slitting mechanism of claim 2 wherein said 5. The slitting mechanism of claim 2 wherein said actuating means further includes a vertically reciprocable pin means movable between upper and lower limit positions connected to said first rack means and extending'coaxially upwardly through the dial assembly of the machine, the arrangement being such that upward movement of the pin means to said upper limit position causes the first cutting element to be fully retracted inwardly out of the line of travel of the fabric being knitted by the machine, while reciprocations of said pin means adjacent said lower limit position reciprocates the first cutting element in the line of travel of the fabric to thereby effect a cutting of the fabric.

6. The slitting mechanism of claim 5 including driving means for the dial assembly and means engageable between said pin means and said driving means for effecting reciprocations of said pin means adjacent said lower limit position.

7. The slitting mechanism of claim 6 including separate control means connected to said pin means for retracting the latter to its upper limit position.

8. The slitting mechanism of claim 1 wherein said first cutting element is provided with a generally vertical cutting edge directed inwardly towards a central portion of the machine, and wherein said second cutting element is provided with a generally vertical cutting edge directed outwardly from a central portion of the machine.

9. The slitting mechanism of claim 1 wherein said first cutting element is provided with a rack means, said actuating means including a pinion for engaging and driving the first cutting element back and forth along an axis which is generally perpendicular to the line of travel of the knitted fabric.

10. The slitting mechanism of claim 9 wherein said second cutting element is in a fixed position relative to said support means.

11. The slitting mechanism of claim 1 wherein said shielding means comprises a collar means carried within the cylinder assembly of the circular knitting machine, and said collar means having a slot formed therein to receive the free end portion of said first cutting element, thereby providing for a shielding of the free end portion of the cutting means as the tubular fabric being knitted descends through an annular space defined between said support means and said collar means. 

1. A slitting mechanism for use with a circular knitting machine having a dial assembly rotatable in unison with a cylinder assembly for cutting a slit along the length of a tubular knitted fabric as the fabric is being knitted by the machine and descends through the cylinder assembly, comprising cutting means having first and second cutting elements which coact to effect a cut in a knitted fabric at a point where the knitted fabric is engaged by said cutting elements, said first cutting element being mounted to reciprocate relative to said second cutting element along a line generally perpendicular to a line of travel of the knitted fabric as the knitted fabric descends past the positions of said cutting elements, support means for suspending said cutting means beneath the dial assembly of the circular knitting machine so that the cutting elements are mounted generally internally of the tubular knitted fabric being produced by the machine, shielding means for shielding a free end portion of said first cutting element from contacting and snagging the tubular fabric being cut, and actuating means operatively associated with the cutting means for controlling cutting functions of the cutting means.
 2. The slitting mechanism of claim 1 wherein said actuating means includes a single pinion means mounted for rotation within said support means, first and second rack means carried within said support means and engaged with said pinion means, said first rack means being mounted on a generally vertical axis on the centerline of the dial assembly so as to impart driving motions to said pinion means when said first rack means is reciprocated on its axis, and said second rack means being mounted on a generally horizontal axis so as to receive driving motions from said pinion means, and said second rack means being positioned to reciprocate said first cutting element.
 3. The slitting mechanism of claim 2 wherein said second rack means is formed as a part of said first cutting element so that driving motions of said pinion means are transmitted directly to said first cutting element.
 4. The slitting mechanism of claim 2 wherein said support means includes a housing for enclosing said first and second rack means and said pinion means, said housing being secured to a bottom surface of the dial assembly of the machine so that said housing and its contained structures can rotate with rotational movements of the dial assembly about its centerline.
 5. The slitting mechanism of claim 2 whereIn said actuating means further includes a vertically reciprocable pin means movable between upper and lower limit positions connected to said first rack means and extending coaxially upwardly through the dial assembly of the machine, the arrangement being such that upward movement of the pin means to said upper limit position causes the first cutting element to be fully retracted inwardly out of the line of travel of the fabric being knitted by the machine, while reciprocations of said pin means adjacent said lower limit position reciprocates the first cutting element in the line of travel of the fabric to thereby effect a cutting of the fabric.
 6. The slitting mechanism of claim 5 including driving means for the dial assembly and means engageable between said pin means and said driving means for effecting reciprocations of said pin means adjacent said lower limit position.
 7. The slitting mechanism of claim 6 including separate control means connected to said pin means for retracting the latter to its upper limit position.
 8. The slitting mechanism of claim 1 wherein said first cutting element is provided with a generally vertical cutting edge directed inwardly towards a central portion of the machine, and wherein said second cutting element is provided with a generally vertical cutting edge directed outwardly from a central portion of the machine.
 9. The slitting mechanism of claim 1 wherein said first cutting element is provided with a rack means, said actuating means including a pinion for engaging and driving the first cutting element back and forth along an axis which is generally perpendicular to the line of travel of the knitted fabric.
 10. The slitting mechanism of claim 9 wherein said second cutting element is in a fixed position relative to said support means.
 11. The slitting mechanism of claim 1 wherein said shielding means comprises a collar means carried within the cylinder assembly of the circular knitting machine, and said collar means having a slot formed therein to receive the free end portion of said first cutting element, thereby providing for a shielding of the free end portion of the cutting means as the tubular fabric being knitted descends through an annular space defined between said support means and said collar means. 